Optical Colonoscopy and Virtual Colonoscopy Numbers after Initiation of a CT Colonography Program: Long Term Data

Abstract

Background & Aims

The effect of CT colonography (CTC) screening on colonoscopy is unknown. The objective of this study is to determine the effect of a CTC screening program on the number of screening, therapeutic and total colonoscopies performed.

Methods

We compared the quarterly mean numbers of colonoscopic examinations performed for 50-79 year olds undergoing colorectal cancer screening in 2003, before initiation of a CTC program, to 2011, seven years after the CTC program began at our academic tertiary care facility.

Results

The CTC program began in 2004 with a peak number of 387 CTC examinations performed in the 3rd quarter of 2005 and 275 examinations in the final quarter of 2011. Screening colonoscopies increased from 555 mean/quarter in 2003 to 1460 in 2011 (P < 0.001). The mean/quarter number of total colonoscopies performed increased from 1104 in 2003 to 2382 in 2011 (P < 0.001). The number of overall colon cancer screening examinations (Colonoscopy + CTC) increased from 555/quarter in 2003 to 1736 in 2011 (P < 0.001).

Conclusions

Since the initiation of CTC screening at our institution, the overall number of total colorectal cancer screening examinations (CTC + colonoscopy) has greatly increased. The initiation of a CTC screening program did not lead to a reduction in the number of colonoscopic examinations performed. Conversely, a significant increase in the number of screening and total colonoscopies completed was observed.

Introduction

Cancer of the colon and rectum continues to be the third leading cause of cancer related mortality for both men and women within the United States [1]. Colorectal cancer develops from adenomatous colon polyps in a complex adenoma to carcinoma sequence that is thought to take approximately 7-10 years [2-5]. Colorectal cancer screening for the detection and removal of adenomatous polyps has been shown to decrease colon cancer incidence and mortality [6-10]. Optical colonoscopy or endoscopic colonoscopy has become the dominant test for colon cancer screening in the United States [11]. Computed tomographic colonography (CTC), or virtual colonoscopy, is an alternative method for detecting colonic precancerous polyps which has the potential to become a significant colorectal cancer screening option for US screening programs [12]. CT colonography has been shown to have similar detection rates as colonoscopy for advanced colonic lesions and large (≥ 10 mm) polyps [13-16]. Since its introduction, there has been a gradual increase in the number of US hospitals adopting CT colonography technology with the desire to provide an alternative colorectal cancer screening modality [17,18]. Furthermore, it has been proposed that CT colonography, due to its less invasive nature compared to optical colonoscopy, would be an appropriate screening option for patients who do not wish to have an endoscopic examination [19]. The impact of CT colonography on endoscopic colonoscopic screening programs has been a topic of speculation, with prior modeling studies suggesting a significant reduction in the numbers of optical colonoscopic examinations performed as a consequence of CTC screening [20, 21].

In 2004, the University of Wisconsin became the first institution in the United States to have third party payer coverage of CTC for average risk colorectal cancer (CRC) screening. The American Cancer Society and American Gastroenterological Association have supported CTC as a screening option and the primary care doctors within the University of Wisconsin Health system have had 7 years with open access to third party covered virtual colonoscopy. The aim of our study was to present long term data, over a 7 year period, on the effect of a CTC screening program on the number of screening, therapeutic and total optical colonoscopic exams.

Methods

In April 2004, the University of Wisconsin Hospitals and Clinics, Madison, Wisconsin began third-party payer covered colorectal cancer screening for average risk patients with CT colonography. The University of Wisconsin Hospitals and Clinics primary care providers can refer patients to be screened with either optical colonoscopy or CT colonography, based on both provider and patient preference with payment covered by the dominant insurers in the area. Both screening modalities use an open access protocol without pre-screening gastroenterology or radiology clinic evaluations. Both screening programs are referred patients from the same population surrounding Madison, Wisconsin and from the same group of primary care providers.

CT Colonography

Patients referred for CTC screening program undergo a pre-examination preparation including a clear-liquid diet the day prior to examination and a bowel preparation including cathartic (magnesium citrate, Sunmark) and tagging agents (2% w/v barium; Bracco and diatrizoate; Bracco). The CTC examinations entails an insertion of a rectal catheter to obtain colonic distension by an automated CO2 insufflator. Multi-Detector acquisitions of single-breath-hold supine and prone images are obtained using a 16 channel CT scanner (LightSpeed Series; GE Medical Systems) [23]. No sedation is used for the CTC examinations. CT image interpretation is performed with a combined 3D “fly-through” and 2D mucosal evaluation with subsequent two-dimensional confirmation of possible polyps (V3D Colon, Viatronix, Stonybrook, NY). All CTC reports are interpreted within two hours of the examination to allow for same day optical colonoscopy if needed. Patients with polyps 10 mm or greater are referred to same day optical colonoscopy for polypectomy. All patients with polyps measuring 6-9 mm in size are offered same day colonoscopy for possible polypectomy versus entering a CTC surveillance program. An imaging surveillance program is available for patients with isolated (1 or 2) 6-9 mm polyps. Polyps ≤ 5 mm in size are not routinely reported in isolation by CT colonography.

Optical Colonoscopy

The day prior to the colonoscopy, patients are asked to start a clear liquid diet at noon. Colonic preparation are usually polyethylene glycol electrolyte solutions taken the night prior to the procedure or in split dose with half the solution taken the night before and half the day of the examination. Colonoscopy sedation generally is performed with intravenous fentanyl and midazolam. Standard colonoscopic screening techniques are used with initial cecal intubation achieved followed by slow colonoscope withdrawal and mucosal inspection for polyps. Once identified, all polyps are removed and sent for pathologic analysis.

Study Design

The purpose of our study was to determine the impact of an insurance covered CTC screening program on the number of screening, therapeutic and total optical colonoscopic examinations performed at our center over a 7-year period. We tracked the number of screening, diagnostic, and total CT colonography examinations and the number of screening, therapeutic (polypectomy), and total optical colonoscopy examinations after the initiation of the CT colonography program began at our institution in 2004. We compared the mean numbers of screening, therapeutic (polypectomy) and total optical colonoscopies performed, per quarter, in 2003, one year prior to the initiation of the CTC screening program, to 2011, seven years after the establishment of the CTC program. Statistical comparisons were made using Student's t-test for continuous outcomes. Statistical significance was considered at a two-sided P value < 0.05. Our study was approved by the University of Wisconsin Institutional Review Board.

Results

The CTC screening program began in 2004, with a peak number of 387 CTC examinations performed in the 3rd quarter of 2005, gradually decreasing to 275 examinations per quarter in 2011. The total number of screening colonoscopies performed significantly increased from 555 mean per quarter in 2003 prior to the initiation of the CTC program to 1460 mean per quarter performed in 2011 (P <0.001). Similarly, the mean number of total colonoscopies performed per quarter, in patients aged 50 -79, increased significantly from 1104 in 2003 to 2382 in 2011 (P < 0.001) (Fig. 1).

Fig 1.

Number of colonoscopies and CT colonographies. Patients age 50-79.

The number of colonoscopies with polypectomies increased significantly from 144 per quarter in 2003 to 536 per quarter in 2010. A majority of this increase was due to the overall growth in the numbers of screening and total colonoscopies performed as there was only an 8 % referral rate from CTC to colonoscopy (for polypectomies) during this time.

The total number of screening colorectal examinations performed, CTC and colonoscopy combined, increased significantly from 555 per quarter in 2003 prior to the initiation of the CTC program to 1736 per quarter in 2011 (P < 0.001). In 2011, 7 years after the initiation of the CT colonography screening program, there were approximately 10,986 colorectal examinations performed at the University of Wisconsin Hospitals and Clinics. Of these examinations, 86.8 % were with colonoscopy, 10.0 % were with CT colonography and the remaining 3.2 % were with other modalities such as flexible sigmoidoscopy or FOBT (Fig. 2).

Fig 2.

Total colorectal screening exams for 2011.

Discussion

Colorectal cancer continues to be one of the leading causes of cancer related deaths in the USA. However, patient screening rates remain poor and only slightly more than one-half of eligible US patients are screened for colon cancer [24-27]. In addition to provider and patient education, as well as improved access, various screening modalities are needed to help improve US colorectal cancer screening rates. It has been proposed that CT colonography would be an appealing screening option for patients who do not wish to have an endoscopic examination and therefore increase overall screening compliance [19, 28]. Over the past decade, optical colonoscopy has been the dominant test for colorectal cancer screening. Some have speculated that CT colonography will significantly decrease the numbers of optical colonoscopies performed. Previous mathematical models have predicted a 9-22% decrease in the numbers of optical colonoscopies completed as CT colonography became more established [20, 21]. To date, however, there have been no large studies evaluating the actual impact of a CT colonography screening program effect on optical colonoscopy screening over a several year time span. In 2004, the University of Wisconsin became the first US institution to have third party payer coverage of CTC screening. Our initial data revealed that CT colonography did not significantly impact the number of screening optical colonoscopies performed, nor the number of optical colonoscopies requested by primary care providers during the first two years of CTC program establishment [29]. However, our previous study only examined data two years after the initiation of our CTC program and we theorized that may have been too short of a time period to adequately assess the impact of CTC locally as providers may not have been familiar with using CTC as a screening modality. Furthermore, there has been a broader acceptance of CTC nationally as a screening examination with more evidence supporting its use [17, 18].

However, after seven years, our current study reveals that CT colonography still has not significantly influenced the numbers of screening and total optical colonoscopies. In fact, the number of optical colonoscopies performed at our center over the last seven years increased significantly and endoscopic colonoscopy continued to be the dominant colorectal cancer screening modality accounting for approximately 90% of patients screened, despite the availability to CTC for patients and primary care providers.

The numbers of CT colonographies completed peaked one year after the initiation of the program and gradually decreased slightly throughout the study time period and has reached a steady state of approximately 250 CT colonography examinations performed per quarter. Conversely, the numbers of screening optical colonoscopies almost doubled during the same time period. During this time period, there was no significant change in the number of academic radiologists reading CT colonographies or academic gastroenterologists performing screening colonoscopic examinations. The reasons for CT colonography not affecting endoscopic colonoscopy is not entirely clear, but most likely reflects that optical colonoscopy and CTC are different tests with relative advantages and disadvantages. Optical colonoscopy itself is a strong colorectal cancer screening modality being the only therapeutic screening test. Optical colonoscopy finds as many advanced adenomas as any screening modality and more overall adenomas than other screening tests [13, 30]. Thus optical colonoscopy is not in need of being “replaced” as a screening test and thus it is unlikely that CTC at present or in the future will replace endoscopic colonoscopy.

Additionally, although our institution has had insurance covered CT colonography locally since 2004 and major societies have supported its use, mixed messages may have affected primary care doctors and how they ordered CT colonography examinations for their patients. The decision of Medicare to not reimburse CTC in 2008, citing insufficient evidence for CTC as a colorectal cancer screening test, and the fact that the USPTF did not recommend CTC as a screening test may have affected ordering providers’ attitudes about CTC [31, 32].

More importantly, the overall number of colorectal cancer screening examinations (CTC + Colonoscopy) performed at our institution significantly increased from 555 per quarter in 2003 to 1736 per quarter in 2011. In 2011, there were 10,986 colorectal examinations performed at the University of Wisconsin Hospitals and Clinics. Approximately 86.8% were with colonoscopy, 10.0% were with CT colonography. Although a majority of the growth in the number of our annual colorectal cancer screening examinations performed was due to an increase in the number of screening optical colonoscopies completed, CT colonography added an additional 900 to 1400 patients screened per year during our study period. These patients might not have otherwise undergone any colorectal cancer screening in the absence of CT colonography. CTC may not replace optical colonoscopy screening, but, instead adds to it. For example, if third party payer coverage is extended nationally and other institutions adopt CT colonography screening as an option, an additional 7-10% of patients could get screened which would greatly increase screening rates across the country.

It was thought that CT colonography would significantly increase the therapeutic colonoscopies and number of colonoscopies with polypectomies performed at our institution by resulting in increased CTC polyp detection and referral to endoscopic polypectomy. Over the seven years studied, the number of therapeutic colonoscopies with polypectomies increased significantly from 144 per yearly quarter in 2003 to 536 per quarter in 2010. However, most of the observed increase was due to the overall growth in the screening optical colonoscopy numbers, as there was only an approximate 8% referral rate from CTC to OC. For example only 18 to 28 patients per quarter (less than 10 per month) were referred to colonoscopy from CT colonography for possible polypectomy. This was primarily due to management of small polyps by CTC, with the majority of the 6-9 mm polyps seen entering CTC surveillance and that 5 mm or less polyps are not referred to endoscopic colonoscopy as they are not routinely reported.

Conclusions

The initiation of a CTC screening program did not result in a decrease in the numbers of colonoscopies performed at our institution in the first seven years since CTC program establishment. Conversely, the number of screening endoscopic colonoscopies performed significantly increased during the study period. Despite previous speculation, CTC has not “replaced” screening colonoscopy and with eight years of experience it is unlikely that it will in the future. CT colonography and colonoscopy continue to be different types of screening examinations each with separate advantages and disadvantages. Most of the screening colorectal examinations performed at our institution continue to be with optical colonoscopy. However, CT colonography provides an important additional screening option for patients and providers. Given the number of years that a third party insurance covered CTC screening program has existed at our institution without affecting endoscopic colonoscopy, it can likely serve as a model that if CTC screening becomes a national test it will not decrease optical colonoscopy but only add to present colorectal screening rates.